Do adult patients with PKU need the strict Phe-restricted diet?

High phenylalanine levels directly affect mood and sustained attention in adults with phenylketonuria: a randomised, double-blind, placebo-controlled, crossover trial. ten Hoedt et al. 2011 J Inherit Metab Dis (2011) 34:165â€“171A randomised double-blind placebo-controlled trial looked into the neuropsychological effects of short-term elevation of Phe levels in adults with PKU. Nine adults with PKU underwent two 4-week supplementation periods: one with Phe, mimicking normal dietary intake, and one with placebo. A set of neuropsychological tests was administered at the end of each period and for each patient a friend or relative, completed weekly questionnaires, evaluating the patientsâ€™ mood. The study concludes that high plasma Phe levels have a direct negative effect on both sustained attention and on mood in adult patients with PKU.Â Â